They need 6 hours of full sun. Avoid overwatering, soil should be moist but never soggy roots.
They don't like it cold or too hot!
Geraniums have moderate fertilization needs -- usually adding a balanced fertilizer, such as a 10-10-10, every two to four weeks is plenty to keep the blooms going. Mix 1 tablespoon of water-soluble fertilizer in a gallon of water -- or follow the manufacturer's directions.